1. Field of the Invention
The present invention relates to a filter device using a detachable roll filter unit and a projection type display apparatus using the filter device.
2. Description of Related Art
Projection type display apparatuses, such as a projector, have been used in a variety of circumstances, home-theater, commercial uses and so on. Projection type display apparatuses include image display elements such as a liquid crystal panel and a DMD (digital mirror device), and magnify and project an optical image formed by concentrating strong light from a light source, such as a lamp, onto the image display elements and modulating the concentrated light in response to an input image signal. The image display elements subjected to strong light, the light source itself, the apparatus power supply, etc. could be damaged by heat unless they are cooled adequately. For this reason, cooling fans that provide a strong cooling effect generally are used in projection type display apparatuses so as to blow air into the apparatuses.
However, when a flow of air is produced by an air blow from a cooling fan, dust in the air enters the apparatus, so that it is necessary to remove the dust by providing the air intake with a filter. However, when the dust accumulates on the filter, the cooling effect drops. Therefore, many projection type display apparatuses use detachable roll filters.
In a case where a detachable roll filter is used, the cooling effect can be kept constant by taking up the filter when a predetermined amount of dust accumulates on the filter. However, since the length of the filter that can be taken up is fixed, the filter needs replacing when it is taken up entirely.
After replacing the filter, it is necessary to reset information on the replaced filter stored in the projection type display apparatus. Specifically, the information includes the take-up amount, estimated replacement time, an error and the like. By resetting these kinds of information, the time over which the new filter can be used can be estimated precisely.
Conventionally, after replacing a filter, the information on the replaced filter has been reset by a user pressing a button for resetting the filter information or selecting reset from a guidance menu displayed by the projection type display apparatus. However, when a user forgets to reset the information after replacing the filter, the time over which the replacing filter can be used cannot be estimated precisely.
As a measure directed to this problem, JP 2006-145053 A discloses a system in which a serial number is read at regular intervals from an IC tag attached to a filter and the filter information is reset automatically when the serial number changes. In this system, when the serial number read from the IC tag changes, the system determines that the filter is replaced and resets the information on the replaced filter. However, even when the replacing filter is not new, the system resets the information on the replaced filter.
Furthermore, the system is not configured to use a rolled filter and it cannot be said that the system is suited for using a rolled filter.